1. Field of the Invention
The present invention relates to a disk drive, a servo control unit, and a control unit, and more particularly to a disk drive, a servo controller, and a controller which have realized high-degree control by lightening processing load to a microprocessor unit (MPU) without increasing cost.
2. Description of Related Art
In hard-disk drives (HDDs) employing magnetic disks as data storage media, concentric circular recording tracks are formed on the magnetic disk. In a conventional HDD, as shown for example in FIG. 2, circular tracks 202 with a predetermined width are formed concentrically on the recording surface of a magnetic disk 201. The recording surface is provided at predetermined-angle intervals with servo areas on which servo patterns 203 are recorded. In addition, between adjacent servo areas there is provided a data sector 205 on which a data area 204 is recorded.
In the aforementioned conventional HDD, if a sector is specified from an outside unit and recording/regeneration is instructed, the head 206 will be moved to a target track on which the sector specified for recording/regeneration has been recorded (seek control). After the head 206 has arrived at the target track, the head position is adjusted so that the head 206 follows the target track (following control). The servo control, such as seek control and following control, is performed by driving a head arm 207 with the head 206 attached thereto by means of a voice coil motor (VCM) 208.
A description will hereinafter be made of the following control.
Each servo sector 303, as shown in FIG. 3, records a cylinder ID number (CYLID) indicating a track number, a physical sector number (SECCNT) indicating a servo pattern number, burst patterns (WEDGE-A, WEDGE-B, WEDGE-C, WEDGE-D) for tracking (following) control, and so on.
The cylinder ID number CYLID is recorded with special notation called a gray number code. Unlike normal binary-coded notation, the gray number code is defined so that each time a value increases by 1, only a single point in a bit pattern changes. In the gray number code, even when the head 306 flies between the cylinder ID numbers CYLIDn and CYLIDnxe2x88x921, either value is always obtained.
The physical sector number SECCNT is a number for identifying each individual servo pattern. Even when the radial position varies, this number does not change, so it is recorded with binary-coded notation.
The burst patterns (WEDGE-A, WEDGE-B, WEDGE-C, WEDGE-D) are magnetic patterns for removing the uncertainty of the cylinder ID number CYLID such as described above, deciding over which track the head is positioned among adjacent tracks, and also detecting a detail position on a track. The burst patterns, as shown in FIG. 3, are recorded so that the radial recorded positions of the burst patterns each having the width of two track pitches as one cycle differ from each other by half the track pitch.
If the head 306 passes over tracks constructed as described above, the regenerated outputs CYLID, SECCNT, WEDGE-A, WEDGE-B, WEDGE-C, and WEDGE-D will appear in this order on the output of the magnetic head 306. The regenerated levels A, B, C, and D of these burst patterns WEDGE-A, WEDGE-B, WEDGE-C, and WEDGE-D change in correspondence with the position of the head 306.
FIG. 4 shows a change in the regenerated level of each burst pattern in the case where the center position of the head 306 (as shown in FIG. 3) changes from one end of a track nxe2x88x921 to one end of a track n+2. Each of the regenerated levels A, B, C, and D changes linearly in correspondence with the position of the head 306 when the head 306 is in a predetermined range. Also, A+B and C+D are nearly constant, respectively. For this reason, from the regenerated output levels of the burst patterns a position error signal (PES) can be detected. On this PES, there are two kinds: a master PES (MPES) employing the aforementioned A and B and a slave PES (SPES) employing C and D. The MPES and the SPES are computed by the following equations:                               M          ⁢                      xe2x80x83                    ⁢          P          ⁢                      xe2x80x83                    ⁢          E          ⁢                      xe2x80x83                    ⁢          S                =                                                                              A                  -                  B                                                  A                  +                  B                                            xc3x97              H                        +                          80              ⁢                              xe2x80x83                            ⁢              h                                =                                                                      2                  ⁢                  A                                                  A                  +                  B                                            xc3x97              H                        +                          80              ⁢              h                        -            H                                              (        1        )                                          S          ⁢                      xe2x80x83                    ⁢          P          ⁢                      xe2x80x83                    ⁢          E          ⁢                      xe2x80x83                    ⁢          S                =                                                                              C                  -                  D                                                  C                  +                  D                                            xc3x97              H                        +                          80              ⁢                              xe2x80x83                            ⁢              h                                =                                                                      2                  ⁢                  C                                                  C                  +                  D                                            xc3x97              H                        +                          80              ⁢              h                        -            H                                              (        2        )            
where 00hxe2x89xa6A, B, C, and Dxe2x89xa6FFh and H is the head coefficient (00hxe2x89xa6Hxe2x89xa67Fh, 7F and vicinity). The value areas of the master position error signal MPES and the slave position error signal SPES are both greater than 01h and less than FFh.
In the case where the magnetic head 306 passes over the center of a track n, A and B become equal to each other, so 2A/(A+B) becomes 1 and MPES becomes 80h. Also, in the case where the magnetic head 306 is offset from the center of the track n in the downward direction in FIG. 3, does not pass over WEDGE-A, and passes over only WEDGE-B, A becomes 0, so 2A/(A+B) becomes 0 and MPES becomes 0h. Conversely, in the case where the magnetic head 306 is offset from the center of the track n in the upward direction in FIG. 3, passes over only WEDGE-A, and does not pass over WEDGE-B, B becomes 0, so 2A/(A+B) becomes 2 and MPES becomes FFh (or CYLID become 00h on a track n+1).
Referring again to FIG. 2, the aforementioned calculation is performed by an MPU equipped in a hard disk controller (HDC)xc3x979, or a digital signal processor (DSP) or an MPU (hereafter referred to as simply an MPU and the like) provided separately from the HDC 209. Also, the MPU and the like compute an operational parameter based on the computed MPES and SPES, compute control data (DACOUT) for driving the VCM 208, based on the operational parameter, and supply the control data to the VCM 208. The VCM 208 changes the position of the head 206, based on the supplied control data. In this way, the head 206 follows the track 202. By controlling the timing of recording/regeneration in such a state, recording/regeneration can be performed on a target sector.
Based on the cylinder ID number CYLID regenerated in the aforementioned way, a track number TRK over which the current head is positioned is detected. Also, the PES obtained in the aforementioned way is added to the track number TRK and the added value is supplied to the HDC 209 as position information (POS) indicating the position of the head.
The HDC 209 generates servo data based on the specified target track and the current head position, controls an operation of the VCMxc3x978, and moves the head 206 to the target track. If the head 206 arrives over the target track, the HDC 209 will execute following control such as described above and perform control of recording/regeneration. An enhancement in the track density and a reduction in the seek time can be realized by executing the aforementioned following control and seek control precisely or at high speed.
However, as described above, in the case where servo control, such as seek control and following control, is performed by the MPU provided in the HDC, if operating speed and control precision are attempted to be enhanced, control load to the MPU within the HDC will be increased. For this reason, there are limits to enhancements in the operating speed and the control precision.
Also, in the case where a DSP or an MPU is provided separately from the MPU provided within the HDC for seek control and following control, the device fabrication cost will be raised to more than necessary, because the DSP or the MPU includes functions not needed for servo control.
It can be seen that there is a need for a disk drive which is capable of enhancing operating speed and control precision without increasing cost.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a disk drive which is capable of enhancing operating speed and control precision without increasing cost.
A method in accordance with the principles of the present invention includes a disk drive including a disk storage medium having a servo area on which servo sectors are recorded and a data area on which data sectors are recorded; a record/regenerate section for performing regeneration of a servo sector recorded on the disk storage medium and also performing recording or regeneration of a data sector; a drive section for controlling a position of the record/regenerate section; a control section for performing at least input-output control of data with respect to external equipment or control of the recording or regeneration of a data sector which is performed by the record/regenerate section; a position information extraction section for extracting position information indicating the position of the record/regenerate section from a regenerated output of the servo sector regenerated by the record/regenerate section; and an arithmetic section provided separately from the control section and for computing servo data for driving the drive section, based on the position information extracted by the position information extraction section.
The arithmetic section includes a plurality of retaining sections for retaining data generated in the interior of the position information extraction section, the control section, or the arithmetic section; an adder; at least two selectors for selecting data which is supplied to the adder from data retained in the plurality of retaining sections, external input, and from data generated in the interior of the arithmetic section; and a hardware sequencer for controlling operations of the retaining sections, the adder, and the selectors. The servo data may be computed by control based on the hardware sequencer.